The evaluation of a deposit and mining project is a continuous process rather than a single act. Changes in budget, evaluation criteria, or in the area of costs and incomes may change results valid up to now and the views on using a deposit. Geological quantities are measurable with the help of geological conclusions and engineering calculations. Raw material reserves and their quality are defined as a substance that can be recovered with profit through current technologies and prices. This definition can result in two misunderstandings: geological reserves and the quality of raw materials are understood as variables not connected with mining activities. However, the quantity and quality of remaining reserves depends on changes in our geological knowledge, changing economic conditions, as well as on the exhaustion of reserves. The quantity of reserves and value of the cut-off grade depends not only on geological factors but also upon the methods of deposit extraction, costs and prices.

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